Lennox LGH094U Unit Information page 68

ADJUST CFM
If a test and balance contractor has not commissioned the
unit, use this section to set supply air CFM.
A-Design Specifications
Use table 28 to fill in field-provided, design specified blower
CFM.
B-Set Maximum CFM
Use table 28 to determine highest blower CFM for appropri­
ate unit. Adjust the blower pulley to deliver that amount of
CFM with only the blower operating. See section 1-UNIT
COMPONENTS; C-Blower Compartment; Determining
Unit CFM.
TABLE 28
Blower CFM Design Specifications
Blower Speed
Heating
Cooling High
Cooling Low
Ventilation
C-Enter Design Specifications Into Controller
Use the following menu to enter the blower design specified
CFM into the Unit Controller. Make sure blower CFM is
within limitations shown in table 29. Refer to the Unit Con­
troller manual provided with unit.
M2 Unit Controller -
Settings > Control > Guided Setup > Advanced Guided Setup
> Setup Equipment >Change MSAV
M3 Unit Controller -
SETUP > TEST & BALANCE > BLOWER >
D-Set Damper Minimum Position
To maintain required minimum ventilation air volumes when
the unit is in the occupied mode, two minimum damper posi­
tions must be set. The Unit Controller will open the dampers
to "Min OCP Blwr Low" when blower CFM is BELOW a "mid­
point" CFM. The Unit Controller will open the damper to "Min
OCP Blwr High" when blower CFM is at or ABOVE the "mid­
point" CFM.
The Unit Controller will calculate the "midpoint" CFM.
Set Minimum Position 1
Use the following menu in the Unit Controller to set "Min
OCP Blwr Low" for the blower CFM below the "midpoint"
CFM. When navigating into this menu, the Unit Controller
will bring on the corresponding blower speed and allow
damper position adjustment.
M2 Unit Controller -
Settings > Control > MSAV > Damper > Low Speed
M3 Unit Controller -
SETTINGS > RTU Options > EDIT PARAMETER > EN­
TER DATA ID - 9 > MIN DAMPER LOW BLOWER = X.X
Design
Specified CFM
TM
Settings?>Yes
%
Measure the intake air CFM. If the CFM is lower than the
design specified CFM for ventilation air, use the Unit Con­
troller to increase the damper percent open. If the CFM is
higher than specified, decrease the damper percent open.
Note - Intake air CFM can also be determined using the out­
door air temperature, return air temperature and mixed air
temperature. Refer to the economizer or outdoor air
damper installation instructions.
Set Minimum Position 2
Use the same menu in the Unit Controller to set "Min OCP
Blwr High" for the blower CFM above the "midpoint" CFM.
When navigating into this menu, the Unit Controller will
bring on the corresponding blower speed and allow damper
position adjustment.
M2 Unit Controller -
Settings > Control > MSAV > Damper > High Speed
M3 Unit Controller -
SETTINGS > RTU OPTIONS > DAMPER > MIN
DAMPER POSITION BLOWER ON HIGH = X.X %
Measure the intake air CFM. If the CFM is lower than the
design specified CFM for ventilation air, use the Unit Con­
troller to increase the damper percent open. If the CFM is
higher than specified, decrease the damper percent open.
Note - Intake air CFM can also be determined using the out­
door air temperature, return air temperature and mixed air
temperature. Refer to the economizer or outdoor air
damper installation instructions.
E-VFD Bypass Option
The supply air VFD is factory-set to by-pass the VFD manu­
ally. To by-pass the VFD and operate the blower in the con­
stant air volume mode, use the following Unit Controller
menu and set to "engaged":
M2 Unit Controller -
Settings > Control > MSAV > VFD Bypass >
M3 Unit Controller -
SETTINGS>RTU OPTIONS>BLOWER>VFD BYPASS
To configure the unit to by-pass the VFD automatically, use
the following Unit Controller menu and set to "automatic":
M2 Unit Controller -
Settings > Install > New M2 > MSAV VFD Bypass >
M3 Unit Controller -
SETUP > INSTALL > PRESS SAVE UNTIL THE
MENU READS CONFIGURATION ID 1 > CHANGE
CHARACTER POSITION 6
MATIC BYPASS OPTION AND SAVE
Caution - Units not equipped with a VFD will be set to Set­
tings > Control > MSAV VFD Bypass > None. The blower
motor could be damaged and/or result in product or proper­
ty damage if the setting is changed to automatic or manual.
Page 68
TH
TO "A" FOR AUTO­